The present invention relates to a liquid filter, in particular an oil filter of an internal combustion engine, having a filter housing having a removable cover and having a raw liquid inlet and a clean liquid outlet, having a filter insert that is situated exchangeably in the filter housing and that separates a raw side and a clean side of the liquid filter from one another, the insert having a hollow cylindrical filter material body enclosed at its end faces by two end disks, the end disk that is the lower end disk in the installed state having a central mounting opening, the liquid filter having a filter bypass valve, for which purpose the end disk that is the upper end disk in the installed state having on its lower side a central valve seat that works together with a valve body, the filter housing further having a central discharge duct for emptying the filter housing when the filter insert is removed, and there being situated in the discharge duct a closing pin that is fixed to the housing in the installed state and that can be axially displaced between a closed position, assumed when the filter insert is installed and the cover is closed, and an open position, assumed when the cover is removed and the filter insert is removed. Moreover, the present invention relates to a filter insert for a liquid filter.
A liquid filter of the type indicated above is known from DE 201 18 683 U1. In this known liquid filter, the closing pin extends from the discharge duct upward into the filter insert, up to the upper end disk thereof. At the upper end of the closing pin, there is situated a valve body of the filter bypass valve, this valve body being axially displaceable relative to the closing pin, and the valve body being loaded with a force that acts upward, i.e., in the closing direction of the filter bypass valve, by a spring supported on the closing pin. Between the filter housing and a lower part of the closing pin there is situated a further spring that loads the closing pin with a force acting upward, i.e., in the direction toward the cover of the filter housing.
In this existing art, it is regarded as disadvantageous that a relatively large number of components, in particular two different springs, are required, resulting in correspondingly high production and assembly costs. Moreover, in this known liquid filter, the use of foreign filter inserts cannot effectively be prevented.